1. Field of the Invention
The present invention relates to optical communication equipment and, more specifically, to micro-electromechanical devices for use in such equipment.
2. Description of the Related Art
Adaptive optics is a field of optics dedicated to the improvement of optical signals using information about signal distortions introduced by the environment in which the optical signals propagate. An excellent introductory text on the subject is given in “Principles of Adaptive Optics” by R. K. Tyson, Academic Press, San Diego, 1991, the teachings of which are incorporated herein by reference.
Interest in the field of adaptive optics has increased in recent years due to the demand for various adaptive optical elements for use in advanced applications such as atmospheric imaging, optical signal processing, optical data storage, high-power lasers, etc. A representative adaptive optical element is a deformable mirror that may be used, for example, in an optical system designed to compensate for signal distortions introduced in an optical fiber. An appropriate sensor measures the distortions and generates feedback for the deformable mirror. Based on the feedback, the mirror is deformed such that the distortions are significantly reduced, thus improving receiver performance.
A typical deformable mirror of the prior art is a deformable membrane, the shape of which is controlled by an array of underlying electrostatic actuators, e.g., electrodes. However, the deformation induced by such actuators is typically unipolar. That is, the electrodes can flex the membrane in one direction (i.e., toward these electrodes) only. As a result, the types of distortions correctable with prior art membrane mirrors are limited. In addition, for a membrane mirror having a lateral dimension of about 100 μm, the maximum deformation amplitude is on the order of 1 μm, which puts a corresponding limit on the range of distortions that can be corrected.